Known in the art is an apparatus for granulating metallurgical melt (cf. USSR Patent No. 1,181,530, Int. Cl. C 04 B 5/02, 1978; Off-Bull. No. 35, 1985).
The prior art apparatus for granulating metallurgical melt, and more specifically, for granulating a blast furnace slag, comprises a hydraulic granulator and a trough for supplying metallurgical melt running thereover. The granulator also has a trough for removing therefrom a mixture of granulated slag and water, i.e. a slurry, into a slurry collector comprising a hopper having a horizontally extending distribution channel having an opening in the bottom part thereof for slurry discharge, the hopper being installed adjacent to the trough.
A rotary driven drum having perforated walls is installed so that its axis extends horizontally. The drum has blades for moving granules during rotation. The blades are secured to the peripheral walls of the drum to extend inwardly of the drum. The horizontal distribution channel is received in the drum.
A tank for collecting water flowing throught the drum perforation is installed immediately under and below the drum. The tank has an overflow device for removing an excess of water when water level in the tank rises above an admissible level.
A vertical plate is installed in the tank, on a cover plate thereof, the lower end of the plate being spaced from the bottom wall of the tank. The vertical plate comprises a skimmer and is used to define a part of the tank in which clarified water is collected after precipitation of solid particles.
A means is provided for discharging granules from the drum, which comprises a conveyor extending substantially inside the drum along its axis immediately above the horizontal slurry distribution channel.
Another conveyor is provided under the conveyor for discharging granules from the drum for conveying them either to a storage place or for shipping.
A forced draft cooling tower is provided for cooling water, the clarified water from the tank being pumped to the cooling tower.
A means for supplying water to the granulator is also provided, which comprises a pump for supplying clarified water to the forced draft cooling tower which is connected to the part of the tank for clarified water defined by the skimmer. Another tank for collecting water flowing from the forced draft cooling tower is installed directly under the cooling tower.
The means for supplying water to the granulator also comprises another pump connected to the other tank for supplying a substantial amount of water to the granulator for the granulation proper.
The granulator, slurry removal trough, slurry collector, and drum are covered by a casing having a vent pipe.
The prior art apparatus for granulating metallurgical melt is rather unreliable in operation as molten metal, slag crust, coke lumps fused with metal, and other materials can get into slag during granulation so as to result in explosions and emergency situations.
This is due to the fact that in case slag containing molten metal, crust, and the like gets through water jets from the granulator to the surface of metal members of structures washed with water, closed water-filled spaces are formed between this surface and the slag impinging thereon, and water, which evaporates momentaneously, causes a explosion which may result in a destruction of the metal structure.
In addition, a rather sophisticated and cumbersome system of recirculation (closed-loop) water supply system is used in the prior art granulation apparatus, which makes it difficult to run the apparatus and increases its size.
Granules produced in the prior art apparatus features a rather high moisture content because of a prolonged time of contact of slag with water during granulation and conveyance of slurry through the granulator, trough, slurry collector, horizontal distribution channel and also due to their relative position.